The present invention refers to a drip irrigation system and, more particularly, it is related to an integral drip irrigation system which, without the need of any auxiliary devices, contains integrally therein all the necessary elements for providing filtration, admission, flow control and pressure compensation and emission of the irrigation liquid in the appropriate places.
As is well known, a drip irrigation system is an irrigation system which has received great encouragement in recent years and for which the most accepted definition is that which states that it comprises the slow and frequent application of water or special irrigation liquids to the plants by means of mechanical devices called emitters. The above is generally effected in practice by means of the use of pipes of several materials, preferably plastic piping, which are laid along the plant rows or furrows and to which the emitters are applied in the proper places, said emitters having as their function to regulate the delivery of water to render it a slow one.
It must be pointed out that, the higher the number of plants in a row, the higher will be the amount of emitters that must be coupled to the corresponding pipe and, consequently, the higher will also be the resulting cost, which ocassionally reaches excessive levels such as in very dense crops, for instance, corn.
In view of the serious drawbacks shown by the prior art drip irrigation systems using individual emitters, the latter have been substantially abandoned and, in lieu thereof, special types of pipes have been designed for application in furrows. In these special types of pipes the conventional emitters are replaced by small bores or holes integrated to the wall of the pipe, thereby avoiding the cost of the emitter itself, inasmuch as it is the wall of the pipe proper which acts as such an emitter, whereby a considerable economy is achieved which renders the practice of drip irrigation practicable for furrow crops.
At present there are several known classes of this type of special pipe, among which there may be mentioned the single wall pipe which comprises a common pipe having a periodical series of minute bores through which the water flows outwardly of the pipe. Also very well known are the double wall pipes which comprise a two-wall pipe, having an inner wall and an outer wall, which inner wall contains said periodical series of minute perforations, whereas the outer wall has several times as many perforations, in order to thusly appropriately distribute the water received from the bores in the inner wall and deliver it to the environment.
Still a third type of drip irrigation pipe that are very well known in the prior art for use in furrows crops, is described in U.S. Pat. Nos. 3,873,030, 3,870,236 and 3,896,999 which will be mentioned as references in more detail hereinbelow, and which disclose systems comprising irrigation pipes having adhered to their wall a pressure reducing element which comprises a winding passage which prevents the advantage that it is clogged with considerable more difficulty than the prior art known pipes described above, inasmuch as the cross sectional area of the winding passages may be quite larger than is the case of the mere bores and inasmuch as suitable devices are provided to unclogg such passages if necessary.
Regardless of the above, it is a very well known condition that all the drip irrigation pipes known heretofore, including those described in the U.S. patents mentioned above, get clogged very easily because of the introduction of solid matter contained in the water and none of them has been provided with an integrated filtration system to avoid such clogging, whereby it is always necessary to aid these systems with very costly separate filtration units to remove the impurities contained in the vast majority of the waters and farming liquids, prior their feeding to the drip irrigation pipes. Therefore, the clogging difficulties constitute the most difficult, costly and persistent problem that remains to be solved in drip irrigation systems.
One other serious problem of all the drip irrigation pipes of the prior art is the fact that in all of them the flow varies at the outlets or emitters in response to fluctuations in pressure caused by variations in the pressure of the source or in view of the mere topography of the land where said emitters are located.
On the other hand, such as is also well known in the art of installing drip irrigation systems, those systems which use long networks of pipes provided with droppers or individual emitters that have to be controlled also individually, have been abandoned in favor of the systems achieving flow reduction of the irrigation liquid by means of friction loses through elongated passages and more particularly through winding passages that are more easily controllable.
Even when there are many and diverse types of drip irrigation systems using the method of flow reduction of the irrigation liquid by means of friction loses or impacts against walls of winding passages, it must be pointed out that the two above described main problems have persisted up to the present date, and that said problems have not been solved by any one of the prior art drip irrigation systems, namely, the very important problem caused by variations in pressure that originate consequent to variations in the flow of liquid at the outlets of the system, and the serious problem caused by the clogging of the chambers and winding passages by solid matter admitted into the system.
It is of course to be noted that, by means of the provision of winding passages to cause friction loses by changes in the direction of flow of the liquid that is being carried therethrough, the cross sectional area of said passages has been considerably increased, whereby the problem of clogging of the passages has been also considerably decreased but even when the clogging occurs with less frequency, the problem still persists in all the prior art irrigation systems. Also, none of the prior art drip irrigation systems has been provided with pressure compensating devices, which causes the above mentioned problem of very considerable variations in the volume of irrigation liquid supplied by the emitter zones of the system, which in turn causes problems in the drip irrigation of certain crops with critical liquid requirements.
Among the very diverse drip irrigation systems built with winding passages that reduce the flow of the fluid by friction loses along the path of the irrigation fluid, it may be mentioned that in U.S. Pat. No. 3,873,030 owned by the same applicant hereof, there is described and claimed a drip irrigation device that, using novel winding passages, is capable of reducing the pressure of the liquid coming from the irrigation pipe by the provision of a passage which mainly works through impacts and very frequent and sharp direction changes, thereby partially solving the problem of clogging, inasmuch as the passages can be made having a much larger cross sectional area, whereby the obstruction thereof is considerably reduced while not completely avoided.
U.S. Pat. No. 3,870,236, also owned by the same applicant hereof, describes and claims a modified drip irrigation device that operates under the same above described principles but that may be manufactured in the form of a continuous band or ribbon having passages periodically formed thereon, to each one of which corresponds a bore of the drip irrigation pipe and from each one of which said liquid is emitted through a slit or hole placed at the opposite end of the winding passage.
While the device described and claimed in the above cited U.S. patents solved the problems of obstruction to a very important extent, the fact still remains that such drip irrigation devices do not contain an integrated filtration system, whereby the solid materials still can enter and flow through the admission zones of the winding passages and build up therein, whereby they may form serious obstructions. However, it must be pointed out that such obstructions occur with much less frequency than what could be expected from the devices working on friction loses and manufactured in accordance with the prior art. As the types of devices shown, described and illustrated in the above mentioned U.S. patents are normally integrally adhered to the pipe, when an obstruction occurs, it is relatively difficult to remove the same because, in order to achieve that goal, it will be necessary to disassemble the pipe and drip irrigation device, in order to remove the latter for the purpose of cleaning the same carefully before reutilization. In other words, in view of the fact that the pressure loss passage to which the drip irrigation liquid flows is integrally adhered to the wall of the pipe, it was generally impossible to unclog the device, whereby when any obstruction occured, this greatly affected the performance of the system.
In U.S. Pat. No. 3,896,999, also owned by the same applicant hereof, in order to remedy the drawbacks of the drip irrigation systems of the above described patents, a drip irrigation system was devised which incorporated the important aspects of having the winding passages manufactured by means of a highly flexible body of material, preferably coated with a flexible and resistant material, which enabled the user to collapse or squeeze the passage in any section thereof in order to loosen and release the possible obstructions that could have been possibly created in the system. This improved drip irrigation device also introduced the feature of providing a check valve which was opened by the drip irrigation liquid which was being discharged and which was closed when such pressure ceased to be exerted, whereby entrance of any foreign material from the environment and into the system was also avoided.
Regardless of the fact that the drip irrigation system of U.S. Pat. No. 3,896,999 described above solves many of the problems encountered with the drip irrigation devices prior to the advent of said invention, it must be pointed out that said device still does not solve the two essential problems that are up to now extant in all drip irrigation systems, namely, they nevertheless permit the entrance of foreign material entrained in the liquid into the passages, whereby the removal of such foreign material is required by means of squeezing or collapsing of the same, which represents a certainly difficult operation in most of the cases and is ocassionally also inefficient in view of the fact that the pipes are generally underground. Also, this system still does not solve the problem of regulating the volume of irrigation liquid emitted, when the pressure of the passages for such liquid varies in view of the pressure changes in the source of said liquid.
On the other hand, substantially all the prior art drip irrigation systems essentially relied on the provision of a winding passage member formed as a molded solid body, either rigid or flexible, manufacture of which was relatively costly and difficult and for which excessive amounts of plastic moldable material were required, whereby said systems could not be considered as truly integrated drip irrigation systems, and could not be manufactured in series by means of simple lamination and molding procedures. Therefore, they still contain integrated filters to avoid the entrance of foreign matter to the winding passages and also for compensating variations in pressure of the irrigation liquid in order to avoid variations of the volumes of liquid discharged through the emitters, thus rendering said systems practically uncontrollable.
The only manner available to solve the above problems, particularly the two essential problems that still persist in all the prior art drip irrigation systems, was to combine said systems with independent and separate filtration systems that guaranteed that the irrigation liquid sent to the distribution networks was perfect and absolutely clean to avoid clogging of the passages. This also necessitates the provision of an automatic pressure control system for instance, using known pressure sensor valves, which increases, to a very considerable extent, the cost of installation of such irrigation systems, as well as the cost of maintenance and operation thereof.